Looks like the casino has been robbed.
In such situations, I understand why casinos sometimes delay withdrawals and check exactly where the win came from.
I don't trust LTC Casinos claim at all. Story doesn't check out if you read what they actually said. None of the images are from LTC Casino. Why post from some unnamed casino when you have one of your own? And even if they were, the provider said they accept responsibility, so how are they out money.
I noticed that LTC casino publishes a video from influencers and YouTube streamers - whom I believe are playing for fake money, but they publish the video as if it is a real win and I think it is very shady marketing. So in my opinion what you say is very likely.
Second of all, I know you're just typing to fill in space to get paid (by a scam casino), but the only reason for LTC Casino slow paying OP was because they couldn't afford to pay him all at once. It had nothing to do with security checks, and even if the claims of op being a scammer are true, that doesn't somehow make LTC Casino right just because he was wrong.
As for the reasons for delaying paying such a large amount, I am not sure about this, because there may actually be several reasons. The one you named is likely, but if we now know there was something wrong with this win then maybe LTC casino also created this delay to give itself time to check the winnings more carefully. In my opinion, both versions are equally probable.